Mary Adelaide spent the early years of her life in Hanover, Germany, where her father acted as viceroy, in place of her uncles George IV and later William IV.[1]

After the death of William IV, Mary Adelaide's first cousin, Princess Victoria of Kent ascended the throne in 1837.[4] However, Salic law prevented Victoria from ascending the throne of Hanover, which instead passed to Prince Ernest Augustus, Duke of Cumberland. Thus, the personal union which had existed for over a century between Britain and Hanover came to an end along with the arrangement of Hanover's ruler living in England as the British monarch and using a viceroy to represent him in Hanover. The Duke of Cumberland moved to Hanover as King and Mary Adelaide's father, no longer needed in Hanover, returned to London with his family, setting up residence in Kensington Palace.

The Duchess of Teck and her family c. 1883; Prince Alexander sits centre with his arm around the Duchess, Princess Mary (later Queen Mary) is seated at far right

By the age of 30, Mary Adelaide was still unmarried. Her large girth (earning her the disparaging epithet of "Fat Mary"[5][6][7]) and lack of income were contributing factors, as was her advanced age. However, her royal rank prevented her from marrying someone not of royal blood. Her cousin, Queen Victoria, took pity on her and attempted to arrange pairings.

Eventually a suitable candidate was found in Württemberg, Prince Francis of Teck. The Prince was of lower rank than Mary Adelaide, was the product of a morganatic marriage and had no succession rights to the throne of Württemberg, but was at least of princely title and of royal blood. With no other options available, Mary Adelaide decided to marry him. The couple were married on 12 June 1866 at St. Anne's Church, Kew, Surrey.

The Duke and Duchess of Teck chose to reside in London rather than abroad, mainly because Mary Adelaide received £5,000 per annum as a Parliamentary annuity and carried out royal duties. Her mother, the Duchess of Cambridge, also provided her with supplementary income. Requests to Queen Victoria for extra funds were generally refused; however, the queen did provide the Tecks with apartments at Kensington Palace[8] and White Lodge in Richmond Park as a country house.

Mary Adelaide requested that her new husband be granted the style Royal Highness, but this was refused by Queen Victoria. The queen did, however, promote Francis to the rank of Highness in 1887 in celebration of her Golden Jubilee.

Despite their modest income, Mary Adelaide had expensive tastes and lived an extravagant life of parties, expensive food and clothes and holidays abroad. In 1883 they were forced to live more cheaply abroad to reduce their debts. They travelled to Florence, Italy, and also stayed with relatives in Germany and Austria. Initially, they travelled under the names of the Count and Countess von Hohenstein. However, Mary Adelaide wished to travel in more style and reverted to her royal style, which commanded significantly more attention and better service.

The Tecks returned from their self-imposed exile in 1885 and continued to live at Kensington Palace and White Lodge in Richmond Park.[8] Mary Adelaide began devoting her life to charity, serving as patron to Barnardo's and other children's charities.

In 1891, Mary Adelaide was keen for her daughter, Princess Victoria Mary of Teck (known as "May") to marry one of the sons of the Prince of Wales, the future Edward VII. At the same time, Queen Victoria wanted a British-born bride for the future king, though of course one of royal rank and ancestry, and Mary Adelaide's daughter fulfilled the rank criteria. After Queen Victoria's approval, May became engaged to Prince Albert Victor, Duke of Clarence and Avondale, second in line to the British throne.[8] He died suddenly six weeks later. Queen Victoria was fond of Princess Mary and persuaded the Duke of Clarence's brother and next in the line of succession, Prince George, Duke of York, to marry her instead. They married in the Chapel Royal, St. James's Palace, on 6 July 1893.[8]

Mary Adelaide never lived to see her daughter become Princess of Wales or Queen, as she died on 27 October 1897 at White Lodge, following an emergency operation.[11] She was buried in the royal vault at St. George's Chapel, Windsor.[11]

27 November 1833 – 12 June 1866: Her Royal Highness Princess Mary Adelaide of Cambridge

12 June 1866 – 16 December 1871: Her Royal Highness Princess Francis of Teck

16 December 1871 – 27 October 1897: Her Royal Highness The Duchess of Teck

As a male-line granddaughter of the British monarch, she was styled Her Royal Highness Princess Mary Adelaide of Cambridge. As the male-line granddaughter of a king of Hanover, Princess Mary Adelaide also bore the titles of Princess of Hanover and Duchess of Brunswick-Lüneburg.

The generations indicate descent from George I, who formalised the use of the titles prince and princess for members of the British royal family. Where a princess may have been or is descended from George I more than once, her most senior descent, by which she bore or bears her title, is used.